1. Field of the Invention
The following disclosure relates to an optical information storage medium system and a method of generating a signal for controlling light power.
2. Description of the Related Art
An optical pickup is used for recording or reproducing of an optical information storage medium, such as a Digital Versatile Disc (DVD), a Compact Disc (CD), or a Blu-ray Disc (BD). An optical information storage medium system, for example, an optical recording device such as an optical disc drive, having the optical pickup performs a recording, reproducing, or erasing operation by focusing light emitted from a laser diode onto an optical information storage medium by using an objective lens. The laser diode is a light source. In such an optical information storage medium system, proper light power must be maintained for exact recording, and output power of a light source needs to be controlled based on a write strategy. The write strategy is an algorithm for recording.
A component used in an optical pickup controls the output power of a light source. The component may be a Front Photo-Detector (FPD) or a Monitoring Photo-Detector (MPD).
Generally, an optical pickup uses an optical divider, such as a beam splitter, to divide a light beam incident to an objective lens, provide some of the divided light beams to a FPD, monitor output light power of a light source in the optical pickup based on the intensity of the light beams incident to the FPD, and control light power emitted from the light source by sending a result of the monitoring back to an optical power controller.
In optical information storage medium systems, in order to improve performance, sensitivity of an output of an FPD is adjusted by adjusting light power. Thus, a Variable Resistor (VR) or a Digital PotentioMeter (DPM) may be used to adjust the output sensitivity.
That is, when light emitted from a light source is converted to an electrical signal by an FPD, a level of the electrical signal may be adjusted to a specific target level by adjusting a gain of an amplifier. The amplifier may be an operational amplifier (OP-Amp), and a VR may be used to adjust the gain. When an output of the FPD, which has been adjusted to the target level, is provided to a Digital Signal Processor (DSP), light power may be adjusted and used based on the adjusted output of the FPD.
Therefore, a separate device, such as a VR, or an expensive FPD including a DPM may be used.
In addition, in such an optical information storage medium system, a separate component must be used to adjust the sensitivity to a target sensitivity, and an adjusted value must be used as it is, so usable signal sensitivity is inevitably limited.